Ask HN: Do you use block diagramming software for your code?

I'm catching myself doing this thing where I write some code, block diagram it then the diagram allows me to get a clearer vision of where my program/script is going. Then I add to the block diagram, then write the corresponding code. This pattern is very very nice!! The problem is block diagramming is slow since I have to toggle between my code editor and use either a diagramming software solution or use an image drawing program. This takes away from the speed of the creative process. I'm wondering if there any solutions for this that make this toggling between "worlds" fast. I might make an simple HTML/Javascript version of this for myself but in the meantime I thought I would ask. BTW this seems like it would make a cool add on for Coda 2,Sublime or other editors.